Field Evaluation of Thin Bituminous Surface Mixes

Abstract

Surface layers for Low Volume Roads (LVR) in India are constructed using open-graded aggregate mixes and a seal coat surface, with the objective of providing an impermeable surface. Inclusion of a thin layer of dense bituminous mix, such as the Bituminous Concrete (BC), as a surface course in LVR can ensure improved performance, especially in regions with heavy rainfall. Laboratory studies conducted on the samples of Open Graded Premix Carpet (OGPC), Mixed Seal Surfacing (MSS), and BC mixes prepared at 50 Marshall blows revealed that BC mixes can be compacted to a much better density, and hence they are expected to exhibit improved moisture resistance, when compared with OGPC and MSS mixes. Present study aims to compare the field performance of newly constructed BC pavement surface with OGPC and MSS, in terms of progression in roughness, texture depth, permeability, and rebound deflection, over a period of 1 year from the date of construction. Rebound deflection data were further used for calculating the effective modulus and effective structural number of the pavement. Since LVR in India is designed based on AASHTO (1993) design philosophy, the concept of structural number was used for evaluating the predicted life of the pavement. Although the construction cost of BC was 20% more than OGPC, due to its higher bitumen requirement, the field performance of pavement with BC surfacing was exceptionally superior when compared with OGPC and MSS surfacing.